Process of rapid edge gluing wood sheets and the product thereof



June 27, 1933.

T. w. DIKE ET AL PROCESS OF RAPID EDGE GLUING WOOD SHEETS AND THEPRODUCT THEREOF Filed Sept. 19, 1929 2 Sheets-Sheet l m 1-- K m AK 0 o B@M o VA kw M w H h, 9

Fig. 1

INVENTORS THEODORE W/LL/AMS D/KEQ CHARLES N. CONE J AT ORNEY June 2?,1933. w BIK A 1,915,134

PROCESS OF RAPID EDGE GLUING WOOD SHEETS AND THE PRODUCT THEREOF FiledSept. 19, 1929 2 Sheets-Sheet 2 ATTORNEY Patented June 27, 1933 UNITEDSTATES PATENT OFFICE THEODORE WILLIAKB D131, NEW WESTMINSTER, BRITISHCOLUMBIA, CANADA,

AND CHARLES N. CONE, O1 SEATTLE, WASHINGTON, ASSIGNORB, BY MESNE ASSIGN-HENTS, TO LAMINATING PATENTS CORPORATION, 01" SEATTLE, WASHINGTON, A

CORPORATION O1 DELAWARE PROCESS OF RAPID EDGE GLUING WOOD SHEETS AND THEPRODUCT THEREOF Application filed September 19, 1829. Serial No.893,884.

()ur invention relates to a process of rapidly edge gluing one sheet ofwood to another sheet of wood, to the product thereof and to the devicefor carrying out the same. Our principal object is to reatly speed upthis operation so as to ma e it possible to do edge gluing continuouslyby machine. The said invention reduces the time for performing a singleedge gluing operation from a period of minutes to seconds, for instancefromtwo to fifteen seconds instead of fifteen minutes or more asformerly. Other objects of our invention are to eliminate the use ofadhesive tape, make it possible to edge glue green veneer as well as dryveneer and produce edge glue-joints so economically that the field fored e gluing is greatly extended and it is thereby made possible tosalvage much material that was formerly Wasted for lack of asufiiciently practical means of uniting narrow pieces into wide sheets.

In the manufacture of plywood, the veneer sheets which form the pliesare flat glued face to face. These sheets may be very thin, evenfive-one-thousandths (5/1000) of an inch.

Particularly is this truein the case of expensive woods. To form a panelof a given width, for example, thirty six inches as is common, sheets ofthat width are frequently selected. However, it is necessary, both toutilize narrow width and to produce s cial figured effects, to edge gluenarrow strlps of veneer to build out the desired width. These narrowstrips would otherwise be wasted. Also, in the manufacture of plywood,it is common ractice to use as the core, an assembly of strips of acheaper kind of wood, or of pieces discarded as face stock on account ofdefects. Thus the core also is a built up structure of edge gluedstrips. The same is frequently true of the backs of panels. 'lhus edggluing is vitally important to the art of manufacturing veneer products.

Heretofore, sheets of dry veneer have not usually been edge glued toeach other directly, i. e., wood to wood union, but have ordinarily beenjoined by means of narrow stri .s of adhesive tape glued to their fiatsur ace along the joint'after the two edges have been broiight incontact. Frequently no further means of joining the edges has been usedand the costly troublesome and unsatisfactory taping method has beensubstituted for the desired end of actually uniting the edges but if anactual union between the edges was especially desired, the tape has beenused as a hinge and the edges bent back upon themselves, wet glucapplied to them, then the edges brought into contact in the originalfiat position and held in contact for the fifteen minutes or morerequired for the wet glue to set. Attempts have been made to eliminatethe tape and glue the edges directly by running them through a scarfingmachine so as to increase the area of contact to which the adhesive isapplied but in this case also wet glues have been used and the time ofsetting before the joint became strong enough to handle has been fifteenminutes or more. Also the wet glues squeeze out of the joint and causeserious trouble. method of very quickly and directly uniting sheets ofveneer with edges of the ordinary right angle form without the use oftape has been greatly desired but has not heretofore been availableneither has it heretofore been possible to edge glue sheets of greenveneer.

But serious objections obtain to taping as follows: When the core ismade up of taped veneer sheets and then expensive wood is appliedthereto for facing, there is an unevenness in the surface over the tapedportion, it being understood that the tape is left in place on thejoint. This unevenness is very noticeable when the face stock is highlypolished-often the tape pattern shows through, even a very slightunevenness being detectable since the polished surface is lightreflecting and with light as a detector, the revealing of slightdifferences in the surfaces is facilitated; also, the weakness of ataped product is objectionable. This weakness is due to poor adhesionbetween the face of the veneer and the paper of the tape, whichelsewhere is wood to wood. There is much difiiculty, and to date it isimpossible to get as strong a bond on the face in a taped product as isdesired. The tape is often perforated to minimize by so much, thisobjection. Apart from any strains in use, mere moisture and temperaturechanges in laminae themselves are apt to rupture a taped product; alsosuch strains often result in the face veneer humping up, which, ofcourse, shows up most conspicuously on a polished surface. When gummedtape is applied, the strips are wet and expanded, therefore when theunit dries out, greater contraction occurs along the taped portion thanelsewhere andso movement occurs there which is not present elsewhere.This results in the distortion in the veneer facing which appears asunevenness in highly polished surface where light effects are prominent,and the smallest flaws are rendered conspicuous.

In the field of green veneer, so far as we are aware, there is no priorart in practlce of edge gluing.

The problems which are spec1al to edge gluing are as follows:

While in ordinary plywood manufacture the time period of setting of theglue is relatively of considerable duration, varying from five to thirtyminutes, in, edge gluing the time period must be reduced to the minimum,i. e., to the order of seconds. Among other reasons quantity productionafter the manner of plywood making, is impossible, each glue joint mustbe individually formed and of course this means practically in one stepbecause repeated handling equally interferes with quantity production.This involves careful consideration of gluing itself under the definiteconditions and environment incident to plywood manufacture.

In edge gluing time is the most important consideration. The glue mustattain its strength very quickly. A glue line becomes strong or-setsimmediately when its moisture content falls to a certain amount. Thisamount varies with difl'erent kinds of glue but each glue will have someamount of moisture below which it is strong enough to stand handling andabove which it is not. When several sheets of wet veneer containing dryglue on the glue lines are put into a hot press the moisture in the woodin general tends to move in a direction perpendicular to the source ofheat, that is, the hot plates.

This is true for all of the moisture except for a certain amount whichis located in the territory adjacent to the edges of the panel. Theresult of this is that a good portion of the glue line, or lines, is agathering point as it were for a considerable amount of the totalmoisture and consequently the moisture content of the glue line remainsat a figure above the figure at which the glue line obtains its strengthor sets. The portion adjacent to the edges of the panel does not becomesuch a gathering ground for the excess moisture because most of themoisture in this territory escapes in a lateral direction. This isproven by the fact that when a panel is taken out of the hot press toosoon the center portion always blisters while the edges remain stuck. Inconsequence of this tendency of the mois- -ture to run away from thesource of heat, the

glue line in a panel is relatively slow in gettin its set, especially inthe center portion.

11 such latitude of operations in ordinary plywood manufacture is notpossible in edge gluin In edge gluing, having in mind the fact t at timeis of great importance, it will be seen that it is very important thatthe glue line is not so situated with reference to the source of heatthat it, the glue line, becomes the gathering ground of the excessmoisture, as it does in hot pressing a panel. This must be obviatedpositively. The moisture of the wood must either escape away from theglue line or at least not in any direction which would throw it into theline. It is a primary purpose of our invention to provide a process ofed e gluing which satisfies these conditions an requirements.

Summarily, in all cases the action of the heat in our process is todrive the moisture away from the glue line. When edge gluing by ourprocess, it is not necessary to continue the application of the heatsufiiciently long to drive the moisture entirely out of the wood, itonly being essential to dry out the glue line itself and a small portionof the immediately adjacent wood. This behavior of the moisture underthe influence of the heat in our process is functionally different fromthe behavior of the moisture under the influence of heat in hot platemethods of making plywood with either wet glues or dry powderedadhesives by fiat gluing, where a layer of face veneer is interposedbetween the source of heat and the glue, and the moisture in the veneer,is driven by the heat towards the glue line, and the glue line is thelast portion of the wood to be dried out and the drying out process isretarded by the indirect application of the heat and the necessity ofdryin out the whole mass. Also in our process o edge gluing, the glueline lies in a plane perpendicular to the flat surface of the veneer andto the source of heat and if the heat is applied by contact the sourceof heat contacts directly with the outer edge of the glue line. Thesefeatures we believe disclose important functional differences betweenour art of edge gluing with dry powdered adhesives and methods of flatgluing with similar material in the manufacture of plywood. They alsoexplain the marked advance of our method over the prior art in thematter of time which is the most vital advantage of our process.

Consequently, it will be seen that the conditions provided for by ourinvention are just the reverse in edge gluing in that the glue line isthe first region to dry out thus getting its set quickly, whereas inpanel gluing with the hot press, the glue line is the last region to dryout. 7

When it is considered that glue gets its set only by reason of havingthe moisture reduced to a certain figure, it will be seen that thedifference in direction in the escape of the moisture becomes a verypractical consideration. If it were purelya drying problem it would notmatter which way the moisture escaped perhaps as long as it was finallyeliminated, but this is not purely a drying problem inasmuch as adhesionbegins only when drying has reached a certain stage. 'lherefore, to getquick adhesion, one must get very rapid drying and must so position theheat and the glue line to be able to efi'cct this. ln plywoodmanufacture, the press members are kept clean of glue by reason of theintervening sheet of veneer, that is, for example, in a hot pressprocess the hot press )late does not directly contact the glueits heatis transmitted through a sheet of veneer. In edge gluing, the glue isexposed and provision must be taken that such glue as is employed iscaused to set without permitting it to smear up the heating means, andthe machinery employed. We have discovered that by following theinvention herein disclosed, that this smearingup problem is overcome.

Combined with this problem of keeping the heating members clean is therequirement of preventing an excess of glue being applied and remainingat the glue line. The squeeze out problem is non-existent in ordinarypanel manufacture by the cold process, but is a real difficulty in edgegluing. While an ample amount of glue must be present to fill theirregular spaces between the adjoining edges of the veneer sheets,yetall excess must be removed to avoid smearing, and our inventionprovides for removing such excess so that these various conflictingconditions are harmonized.

Even though the hot means contacts directly the glue exposed along theglue line, we provide for keeping the source of heat clean and fordriving the moisture in a lateral direction, that is, perpendicular toand away from the glue line.

Pressure sufficient to make contact must be applied and yet in edgegluing, where single thin sheets are involved, buckling of the sheetsmust be avoided, so the pressure must be relatively small as compared tothat employed in plywood manufacture.

Again, the time during which pressure must be applied must be reduced tothe order of seconds, i. e., the period of setting of the glue must bevery short in order to make production in the necessary quantity ossiblesince single sheets are dealt with 1n e ge gluing, i. e., the operationin edge gluing is individual. In problem is the controlof penetration ofthe glue, while in edge gluing, the problem is the control of the timeperiod. A quick bond is a vital factor in edge gluing because pres surecan only be applied to one unit at a timea rack of sixty edge gluedjoints is impossible.

Also, in edge gluing, the quantity of glue applied and left in placemust be. just enough to form a film and substantially fill the spacebetween the adjoining faces-all'surplus glue plywood manufacture,thedered unnoticcable or as inconspicious as possible. In plywoodmanufacture, the squeeze out of the glue is immaterialit simply runs outon the edges which are trimmed oil' in shaping and sizing the panel, butin edge gluing there. is no sha ing and sizing operation. A surplus ofglue in edge gluing operates to gum up the machine.

A very essential feature of our invention is that it enables us toprovide a joint with clean faces entirely free from the smearing of theflat surfaces and squeezing out of liquid glue from the joint that hasbeen the characteristic of previous methods. It is well known in the artthat the smearing tendency of wet glues has been a serious obstacle. tothe development of machinery for edge gluing. Since in our method the)resence of the glue substance is entirely con 'ned to the contactingedges and it is only rendered plastic and not liquid, we avoid thesetroubles completely and this cnables us to develop mechanism forperforming a repetition of an indefinite number of rapidly performed andrepeated edge gluing operations without encountering the (liiiicultiesof the glue smearing the machine or product.

In plywood manufacture with the hot press, the entire moisture of bothsheets is involved in the glue problem, while in edge gluing only theportion of the sheets immediately adjacent the glue line is involved,the heat driving the moisture towards the glue line in plywoodmanufacture, while in edge gluing the moisture is driven from the glueline. Here again then, we have a different problem to meet in providingfor the plasticizing of the 1%, which means sufficient moisture must liepresent. Too much moisture delays the setting period.

It is to be noted that in any gluing operation it has been heretoforenecessary to apply pressure upon the bodies being joined so as to obtaingood contact between the surfaces being glued, and to maintain thispressure until the bond is sufficiently set so that the body formed canbe handled without disrupting the bond. It is desirable to shorten asmuch as possible the period of time during which it is necessary tomaintain this pressure. This is especially true in edge gluing, i. e.,in forming bodies of which the plane of the largest surface issubstantially perpendicular to the plane of the joints, for the pressuremust be applied in a direction substantially perpendicular to the planeof the ioints, and since this is the direction of the argest dimensionof the bodies it is obviously not practical to apply the pressure uponan assembly of bodies of this nature, the pressure being transmittedfrom one body to another as 1s common practice in making plywood. Forthis reason pressure must be applied and maintained separately upon eachbody to be formed and the shorter the time during which pressure must bemaintained the less equipment and space will be required for thispurpose. It is often very desirable to accomplish the whole gluingoperation in one machine. In order to make this possible it is necessarythat the time be very short during which the body being formed must bekept under pressure and the shorter is this time the greater will be thecapacity of the machine and the more simply it can be constructed.

The length of time during which it is necessary to maintain pressuredepends upon the rapidity with which the glue sets.

In gluing, in general, the formation of a glue bond depends uponbringing the glue into a plastic condition in place between the surfacesto be joined so that good contact is obtained between the glue substanceand the surfaces to be joined, and setting the glue in place while thecontact is maintained by the application of pressure. In the commonmethods of gluing, water, or some other liquid of a solvent nature, isused to bring the glue into a plastic condition and the glue is set inplace by the removal of the water or other liquid from the glue. Therapidity with which the glue sets depends upon the rapidity with whichthe liquid can be removed from it. The less liquid the glue contains,the more uickly can the liquid be removed from it so that it will be setand the bond will be formed.

In the methods of gluing in common use, the glue is applied in the formof a colloidal dispersion of the glue in a liquid. In order that such aglue may be applied it must have a certain degree of fluidity, and sinceits fluidity depends upon the proportion of liquid to glue, a certainminimum amount of liquid must be used in order to impart to thedispersion sufiicient fluidity so that it can be applied.

We have provided a process for overcoming these difliculties and forcarrying out these objects which consists of a combination of aparticular condition of glue, a method of supplying the necessaryplasticizing liquid, together with a step of removing from the portionof the faces adjacent to the joint any accidental glue in contacttherewith, together 'with a method of freeing the adhesive on the edgejoint of the excess of water so that it acquires sufiicient strength topermit handling very quickly.

The above mentioned general objects of our invention, together withothers inherent in the same, are attained by the device, illustrated inthe following drawings, the same being preferred exemplary forms ofembodiment of our invention, throughout which drawings like referencenumerals indicate like parts:

Figure 1 is a plan view of a machine in which our invention may beapplied;

Fig. 2 is a view in side elevation of the same;

Fig. 3 is a view in end elevation of the same;

Fig. 4 is a plan view of a modified form of the same wherein the heatingmeans is moved over the panel;

Fig. 5 is a view in side elevation of the machine shown in Fig. 4;

Fig. 6 is a view on line 6, 6 of Fig. 4;

Figs. 7 and 8 are views in plan and section of a modified form of theheating means, i. e., an electrically heated shoes; and

Fig. 9 is a fragmentary view of still another modified form of theheating means comprising an electrically heated wire operating as aradiator.

Two sheets 9 and 10, of wood or veneer, one of which has been contactedwith adhesive 1n discrete particle form in the presence of aplasticizing liquid as by dampening with a plasticizing liquid anddipped into the adhesive material in the form of 'dry or discreteparticles, are brought together on a supporting surface 11 of theassembling table 12. These sheets may be pressed together by resilientlymounted rollers 13 operating against guide rollers 14. Any excessadhesive material accidentally lodged upon the faces of the sheets ofwood, being dry, is readily removed by any suitable means as an airblast from nozzle 15, so that all smearing of the machine and face ofthe panel is avoided.

The sheets 9 and 10 then pass between heated rollers 16 and 17, thelatter being driven by motor 18. These rollers may be steam, gas orelectrically heated. Upon passing the rollers 16 and 17 the two sheets 9and 10 are edge glued together into a single panel, the glue having beenset in the time required for it to pass through the rollers, i. e.,substantially within a few seconds, so that the process is continuous,one set of sheets following the other progressively through the heatingrollers 16 and 17.

In the modified form shown in Figs. 4, 5 and 6, the sheets of wood 19and 20, prepared as specified for sheets 9 and 10 as respects adhesivematerial and plasticizing liquid, are brought together on supportingsurface 21 of heated table 22 and heated roller 23, mounted in carriage24 on rail 25 is rolled over the adjoining edge portions of the sheets.The carriage 24 may be reciprocally moved by chain 26 operating oversprockets 27 and 28, said chain being actuated by motor 29. Even withouthaving the sheets subjected to laterally directed pressure during theheating operation, we have found it possible to edge glue the sheets.

Instead of heating rollers, the heating means may be in the form of anelectrically heated shoe, disposed for relative movement as respects thesheets. Or the heatin means may be an electric conductor in wh1ch heatvention, we use the adhesive in the dry pow-.

dered or discrete particle form when spread. Water for plasticizing theglue may be either in the wood by reason of the wood being in its greenstate (that is, the water never having been dried out) or else if thewood is dry to start with it is previously moistened in sutlicicntumountfor plasticizing the glue.

This veneer sheet may then be dipped in the dry adhesive to pick up suchquantity of dry glue material as may be caused to adhere thereto, therest falling ofl by gravity. This is one way by which the adhesive in aredetermined amount may be applied. oreover, because of the fact thatthe glue is thus applied in the dry state any accidental particles whichlodge on the faces can bereadil removed either by brushing or blowing 0or by other appropriate means so that the faces are left in a cleancondition as far as any glue is concerned, at the same time leavin allof the glue desired in the joint. Acci ental is used to include idea ofadding a surplus in the first instance to insure substantially fillingthe space between the edges to be joined.

In order for glue to set or attain strength enough to bear handling, theWater, as more fully explained above, in the glue must be reduced to acertain percentage (which percentage varies with difierent glues). Ifthe water is above this per cent the glue will not have strength. Thatis, there must first be suflicient Water present to plasticize the glueand then this water must quickly be removed in order to get a quick set.Therefore, in order to make a glue set quickly it is necessary to removethe Water quickly. In order to accom lish this We position the source ofheat so t at the water is driven out of the glue in the shortestpossible time, that is, so that the water is not driven toward the glueline but is driven away from the glue line.

The use of the dry glue and the fact that the faces adjacent to the glueline are clean enables the source of heat to be applied directly to theedges of the glue line. While in edge gluing as heretofore practiced,the glue in solid form is caused to become plastic, then fluid, thenplastic and then a solid, in our process of edge gluing, the glue iscaused to pass directly from the solid form to the plastic for a periodof time of the order of seconds-and then caused to become a solid.

It will be understood that in this process we are unable to use theamount of pressure that is commonly applied in Wood gluing in general.Such pressure, as is explained elsewhere would cause the sheets tobuckle and become unmanageable. Our process there fore has to reckonwith the slight amount of pressure that we are able conveniently to use.

In carrying out our invention we mafy start with either green veneer orsheets 0 wood or dry sheets or veneer. In practicing our invention withdry veneer we first moisten at least one of the edges which are to bejoined by any convenient means as for instance contacting'the edge withthe surface of a cloth covered roller which is kept saturated withwater. We then contact at least one of the moistened edges with asuitable dry adhesive in powdered form as for instance powdered casein.This may be done by various means for instance by blowing the powderedadhesive against the moistened edge or by contacting the moistened edgewith a mass of powdered adhesive in a container or with a thin film ofthe same spread out upon a flat surface. In any case the moisture on thesurface of the wood causes a sufficient and fairly definite amount ofadhesive to adhere and as the edge is the only portion that is wet weeasily remove accidental glue from the flat surfaces by a jet of air orby brushing or other convenient means. We then brin the edges to bejoined into contact and wliile maintaining sufficient pressure to secureintimate cont-act between the edges, ap ly heat preferabl 'by contactwith a heated metal surface along the joint to be formed, in a directionparallel to the glue line and the heat flowing in a directionperpendicular to the flat surface of the veneer. The pressure to securecontact between the edges while the heat is being applied may be securedby any convenient. means. We have found in practice that the joint canbe formed and set almost instantaneously, a matter of two to fifteenseconds sufiicing for the performance of the steps mentioned and theformation of a secure joint.

In order to edge glue dr veneer-at maximum speed by this method 1t isessential that a very small amount of moisture be applied to the edgesand that the subsequent o erations of applying the powdered glue ansetting the joint be performed immediately afterwards as the moisturewhich is available in contact with the particles of glue ismosteflicient in influencing the formation of the joint, while moisturewhich has been absorbed away from the edge into the structure of thewood has but little influence. If the operation of pressing is delayedthe moisture is allowed to absorbaway from the edge into the wood andthere may not be enough remaining in contact with the glue to form a'oint. In respect to the amount of glue su stance required we have foundthat the amount of adhesive particles ground to a fineness of 40 mesh orfiner which will adhere to a moist wood surface is suflicient to producea satisfactory joint. In regard to the heat it is necessary that theheating element be heated considerably above the boiling point of waterand we have found in practice that if it is heated to a temperature of250 F. a satisfactory joint is produced in a few seconds. It isnecessary also that the heating element remain well above 212 during thecontact in order to dry out the glue joint rapidly.

In performing our invention on green veneer the operations are similarbut owing to the green veneer being already moist it is not alwaysnecessary to apply additional moisture by contacting it with the wetsurface of the roller. In many cases however, the extreme edge of theveneer will have dried out somewhat and the contact with the wet rolleror other moistening means is desirablc to insure that the edge besufiiciently moist. The only other difference when using green vener isin the duration of the application of heat, it being essential thatsufficient heat be stored in the heating medium to dry out locally thenarrow portion of the two sheets of veneer immediately adjacent to theglue joint. In any case the glue joint is formed by the same mechanismas in the previous instance, but the a plication of heat must becontinued for a ew seconds longer because of the greater amount ofmoisture to be removed.

Also, in edge gluing green veneer we prefer in practice to use anadhesive substance l ke powdered casein which becomes relatlvelynsoluble after being set by heat as this avoids danger of the glue jointbeing destroyed by contact with moisture derived from the wet veneer. Asin edge gluing wet veneer by our method only a very narrow strip closeto the glue joint is dried out by the heat, it frequently becomesmoistened again in a short time but if glues of the character describedare used the joint is not injured. Thus in edge gluing with waterresisting adhesive in accordance with our invention, it is not necessaryto dry out any large mass but merely the glue line itself and theimmediately adj acent wood. Furthermore, the moisture need only bedriven from the glue line. As the surface united and consequentconsumption of glue is relatively small in the art of edge gluing thecost of the adhesive is of little account and hence the more expensive.and highly water-resistant adhesives may be used as desired.

With dry fir veneer one-sixteenth (1/16) of an inch thick we find thatthe application of heat requires about two seconds and with green veneerabout five seconds so that in either case the operation is performedwith great rapidity and the quick edge gluing of green veneer offers nosubstantial difiiculties over dry veneer. With conveniently arrangedmeans for moistening the edges, applying the powdered adhesive, removingaccidental excess and applying the pressure and heat, the entireoperation either with wet or dry veneer of considerable thickness iseasily performed in fifteen seconds and in many instances with theordinary thin sorts of veneer can be performed in two or three seconds.The matter of speed in our process is of first importance both becausethe time element in processes of this nature is a measure of the cost,and because we are able to reduce the time element to such a low valuethat if desired the setting of the joint may take place progressivelyalong its length and not simultaneously throughout, as for instance, bythe action of a heated roller previously mentioned, slowly travellingalong the joint and leaving the joint dried out and set behind it. Theoperation may also be performed progressively in the reverse manner withthe veneer in motion and the source of heat stationary. This featurefacilitates the performance of edge gluing with high efiiciencymachinery.

The great saving in time by the use of our process is due not only tothe fact that we do not have as much water to dry out of the glue jointbut is further due to the fact that because of the methods that weemploy we are enabled to do the gluing operation mechanically or in acontinuous manner, thus effecting a further great saving of time.

Our invention is the reduction of time in two ways, 1) we reduce thetime by reason of not having so much moisture to dry out and (2) wereduce the time by providing means by which this gluing can be done in acontinuous or mechanical manner.

The reason why we can do edge gluing mechanically and continuously, thusefi'ecting a great saving in time, is because we eliminate thissqueeze-out of excess glue. This squeezeout has heretofore been a bar tocontinuous and mechanical methods of edge gluing because of the smearingboth of the faces of the stock being glued and of the machine.

In the above we have described and set forth our invention with thepressure reduced to an amount that is suflicient to bring t e edges ofthe sheets of veneer into contact. However. our invention goes furtherand we have discovered that we may edge glue without employing anypressure whatever and particularly without maintaining pressure at thetime the ioint is being formed.

The significance of the elimination of pressure appears in that it isevident that there is a sufficient plasticity or flowing of the adhesiveby the heat in edge gluing, according to our invention, so that eventhough the edges are not actually contacting, nevertheless they may bebound.

Our experience leads us to the conclusion and we suggest that theexplanation is that the mass of the adhesive which will become plasticswells or expands, thereby establishing the bond in contact with theedge even when they are not in contacting relation.

As rior art edge gluing has commonly require( upwards-of fifteen minutesfor the formation of the joint, the gain in time by our method is verygreat. We believe we are the first to edge glue green veneer and alsothe first to edge glue dry veneer in a period of time measured byseconds rather than minutes.

When the glue is applied in the dry powdered form and heat is used, itcan be brought into a state sutiiciently plastic to form a bond,with avery small amount of liquid. Because a very small amount of liquid isused it can be quickly removed, and therefore by our invention a bondcan be obtained in a very short period of time. It is understood thatthe glue does not need to be absolutely dry, but so long as it can behandled in powdered form it is dry enough.

It is possible to use less liquid in our process of gluing because it isnecessary to use only enough to make the glue sutliciently plastic toform a bond under the influence of heat, while in the method of gluingin common use in which the glue is dispersed in the liquid before beingapplied, it is necessary to use enough liquid to bring it into a statesufiiciently plastic or fluidso that it can be applied. It requires moreliquid to bring glue into a state sufiiciently fluid to be applied thanis required to bring it into a state sufficiently plastic to form abond. For instance, less than one part of Water to one part of casein isrequired to bring it, under the inlluence of heat, into a conditionsutliciently plastic to form a bond, but if one part of casein isdispersed in one part of water by the use of caustic soda or some othermethod 3 of dispersion, it will form a tough dough or jelly which isimpractical to spread uniformly upon the surface to be glued.

The benefits of our process of gluing can also be obtained by applyingthe glue in the form of a powder suspended in a liquid and using heat.By suspension we mean a state or condition in which the particles do notdissolve or form a colloidal dispersion in the liquid. A mixture of aproportionally small amount of water and a powdered glue material in thesuspended condition does not become cohesive or doughy and remains in acondition in which it can be applied. It is not necessary to spread thedry adhesive and plasticizing liquid separately. It is also possible forenough of the plasticizing liquid to be absorbed or imbibed in theparticles of adhesive, and for both of them to be spread at the sametime, as discrete particles.

In regard to the character of the adhesives which can be employed wehave found that a wide range. of materials may be used and that any ofthe common adhesives which are rendered plastic by a small amount ofmoisture, equal to approximately one-quarter or onehalf the dry weightof the adhesive in the presence of heat, and are readily dried out to astrong horny condition by the removal of the moisture by the furtherapplication of heat, may be. used. this included practically all commonadhesive material such as animal glue. various raw and modifiedstarches, dried blood albumen. wheat gluten, casein, soya bean flour andother vegetable protein containing substances as well as naturalsubstances containing mixtures of protein and starches such as wheatflour, corn meal, and similar products. Silicate of soda in powderedform may also be used but is not reliable through tendency torecrystallize and lose its adhesive qualities and throu h its highdegree of alkalinity causing staining of the veneer. i

Raw starch flour is an example of an adhesive material suitable for thisprocess With which a suspension can be formed with a proportionallysmall amount of water. Dry powdered casein is an example of ana dhesivematerial which will absorb an amount of water sufficient to make itplastic (under the influence of heat) and still remain in a condition inwhich it can be spread as discrete particles.

However, we are not confined to the use of the above mentioned materialsbut can use any adhesive material that under the influence of heat and aliquid, or heat, a liquid and the action of chemicals, will becomesuiticiently plastic to make good contact with the surfaces to bejoined, and will adhere to these surfaces and when the liquid is removedwill form a strong transversely continuous film bonding together the twosurfaces to be joined. That is, our new method of applying heat andpressure to the forming of joints enables any kind of matter to bejoined with appropriate adhesives, and oined very quick- 1y. so that itmakes possible continuous methods for oining.

Our method of gluing can be used to join together pieces of which thesurfaces to be jo ned are not substar-itially plane surfaces. All thatis necessary is that the surfaces to be joined be of such a nature thatgood contact can be obtained between them by moderate pressure. This isuseful in joining split or torn veneer. The source. of heat should be atleast wide enough to cover the glue line throughout the. greater part ofits length.

it is possible and sometimes desirable to me with the dry adhesivematerial chemicals in a dry powdered form. For example, if the adhesiveused is casein and it is desired to have it become plastic by the use ofless heat, this can be accomplished by compoundautomatically pulling oifall excess.

ing with the dry powdered casein, sodium fluoride and lime. When thismixture ecomes wet the sodium fluoride and lime react to form causticsoda, which helps to bring the casein into a plastic condition.VVaterproofing agents like paraformaldehyde in powder form orformaldehyde in solution may be used either mixed with the adhesive orin solution in the moistening Water for the purpose of rendering thejoint more insoluble, as for.instance paraformaldehyde with animal glue.Also, chemicals can be used in solution in the liquids used, forinstance caustic soda in water. Also, if the powdered adhesive isapplied in suspension in a liquid, chemicals can be added in solution inthe liquid, as for instance formalin can be used in a suspension ofcasein in water, to Improve the water resistance of the bond formed.

We have found also that by adding dispersing agents such as caustic sodaor a mixture of lime and sodium fluoride to the moistening water or as adry powder reagent to the adhesive powder the amount of moisture andheat required to plasticize the adhesive and produce a satisfactory bondmay be materially reduced and the time of forming the bond shortened.

In practicing our invention, suflicient liquid must be present at underthe influence of heat, or heat and the action of chemicals, the gluewill become sufficiently plastic to form a bond. The liquid need notnecessarily be water. For example, alcohol and acetone both have similarplasticizing effects. These liquids are volatilized more rapidly thanwater and hence speed up operation. The liquid can be applied bysponging or sprinkling it on to one or both of the surfaces to be joinedeither before or after the dry powdered glue is applied. However, whenit is applied before the dry powdered glue, it helps to hold the gluepowder in place. When water is the liquid used the pieces to be joinedcan be glued in the green or undried state if suflicient heat is used todry out that part of the pieces immediately adjacent to the gluedsurfaces so that the liquid will be removed from the glue.

The dry powder can be applied by dusting it on to one or both of thesurfaces to be 'oined, or by bringing the moistened surface into contactwith the powder so that some of the powder will adhere to it,gravitySufficient heat must be applied to bring the glue, under the influenceof the liquid or the liquid and chemicals, into a sufiiciently plasticcondition. The heat may be applied by directly contacting a source ofheat such as a steam heated metal plate with the surface of the bodybeing joined, the plane of which intersects the plane of the joints. Theheat the joint so that may also be applied by radiation from a source ofheat upon the body being joined.

The radiator may be substantially a plane surface, as for example theradiating surface of an electric hot plate, a grid of hot wires, acollection of gas burners, or it may even be substantiall a line, forexample a single hot wire, or a ot pipe.

In any case the radiator, if radiant heat is to be used, will be locatedas close as is practicable to the glue line, or may be applied directlyin contact with the edge of the glue line. If a plane, it will besubstantially at a right angle to the plane of the glue ine If thesource of heat itself is linear in na-' ture, as a hot wire, it will beroughly in the plane of the glue line.

In any case, the direction of transmission of heat to the glue line willin general be in the plane of the glue line, or substantially so; ascontrasted with the use of a hot press Where the direction oftransmission of heat {o the glue line is perpendicular to the glue ine.

The limitation to these methods of applying heat is that there must notbe so great a thickness of any portion of the body being joinedinterposed between the source of heat and any part of the surfaces beingjoined that the heat cannot penetrate sufliciently to make the glueplastic. This is to be borne in mind when choosing the direction of heattransmission and the surface of a composite body to which the heat is tobe applied. By glue line we mean the joint or plane of uniting of thebodies or pieces joined.

With less expensive woods, the advantages of the present invention aregreater because the cheapness of the reclamation enables salvaging muchwhich could not be thought of in the taping process. As the edge gluingof veneer is the principal means for producing wide surfaces of thinwood in the manufacture of plywood and also in veneering furniture it isa fundamental factor in the economy of utilizing such products. A largeproportion of the sheets produced when the veneer is out are eithernarrow in themselves or else made narrow by the chopping out of defectsand without edge gluing most of this narrow material would be wasted,hence the usefulness of means of performing edge gluing with rapidityand consequent economy is self evident. As our method of edge gluing ishighly successful with green as well as dry veneer further importantindustrial savings are derived from this feature. Up to 0 the presenttime most veneer has been dried before using and hence the art of edgegluing has heretofore been applied only to dry veneer but since methodsof manufacturing plywood by simultaneously drying and flat gluingtogether sheets of green veneer have now come into common use, it isobvious that further economies are effected by our discovery of apractical method of edge gluing green veneer. As illustrative of this,suppose, for example, we have a two foot wide piece all clear except twolarge knots, one and onehalf inches in diameter and six inches from eachedge. Such a piece of veneer would be first condemned to the grade ofcore stock. However, experience shows that in puttin this strip throughthe dryers, the knots fal out and hence the whole piece is discarded onaccount of three inches total of knots. With our invention, the twostrips in which the knots occur may be chi ped out, and the threeremaining pieces e ge glued to form a veneer sheet, twenty-one incheswide, and raise the piece to face stock grade. This is possible becausestrips only three inches wide may be profitably edge glued by ourinvention, while the present practice is to waste such a piece describedabove. Thus, we reduce the waste to a mere cutting out of defectivestrips as opposed to wasting large pieces. At the present time, thepotential width of the clear stock is the measure of use of the sheetbut with our invention, actual width of the defective portions becomesthe measure of wastage.

Ubviously, changes may be made in the forms, dimensions and arrangementof the arts or my invention, without departing trom the principlethereof, the above setting forth only preferred forms of embodiment.

W e claim:

1. The process of rapidly edge gluing one sheet of wood to another sheetcomprising contacting one of the edges to be joined with undisperseddiscrete articles of adhesive in the presence of sufiicient liquid toplasticize the adhesive material; bringing together the edges to bejoined on a supporting surface; and applying heat directly to the glueline, whereby the moisture is driven away from the glue line.

2. The process of rapidly edge gluing one sheet of wood to another sheetcomprising contacting one of the edges to be joined with undisperseddiscrete particles of adhesive in the presence of suiiicient liquid toplasticize the adhesive material; bringing together the edges to bejoined on a supporting surface; and simultaneously applying heat andpressure directly to the glue line, said pressure being applied to adegree whereby contact is established between the adhesive and thesurface being joined, and said adhesive is rendered plastic and causedto set quickly, whereby the moisture is driven away -rom the glue line.

The process of rapidly edge gluing one sheet of wood to another sheetcomprising contacting one of the edges to be joined with undisperseddiscrete particles of dry adhesive in the presence of sufiicient waterto plasticize the adhesive material; bringing together the edges to bejoined on a supporting surface; and a plying heat directly to the glueline, where y the moisture is driven away from the glue line.

4. The process of rapidly edge gluing one sheetof wood to another sheetcomprisin contacting one of the edges to be joined with undlsperseddiscrete particles of dry ad= hes1v e 1n the presence of sulficientwater to plasticize the adhesive material; bringing together the edgesto be 'oined on a supportmg surface; and simultaneously applying heatandpressure directly to the glue line, said pressure being applied to adegree where y contact is established between the adhesive and thesurface bein joined, and said adheslve is rendered plast1c and caused toset uickly, whereby the moisture is driven aw5ayTl11'om the glue;line.d1

e process 0 ra i ed e luin one sheet of wood to anot er hee t c dmpfisincontacting one of the edges to be joined wi undispersed discreteparticles of dry adhesive 1n the presence of sufiicient water toplasticlze the adhesive material; removing accidental glue; bringingtogether the edges to be ]o1ned on a supporting surface; and applyingheat directly to the glue line, whereby the moisture is driven away fromthg g llue line.

he process of rapidl ed e luin one sheet of Wood to another shee t compr isin contacting one of the edges to be joined wit undisperseddiscrete particles of dry adhesive 1n the presence of suflicient waterto plasticize the adhesive material; removin accidental glue; bringingtogether the e ges to be joined on a supporting surface; andsimultaneously applying heat and pressure directly to the glue line,said pressure being applied to a degree whereby contact is establlshedbetween the adhesive andthe surface being joined, and said adhesive isrendered plastic and caused to set quickly, whereby the moisture isdriven away from the glue line.

7. The process of rapidl ed e luin one sheet of wood to another cd mprisihg pr ivid- 111g one of the edges to be joined with undis= perseddiscrete particles of adhesive in the presence of sufiicient water toplasticize the adhesive material; bringing together the edges to bejoined; and applying heat to the edge portions being joined duringrelative movement between the sheets and the heating means, whereby theedge gluing operation is rendered continuous.

U 8. The process of rapidly edge gluing one sheet of wood to anothercomprising contacting one of the edges to be joined with undisperseddiscrete particles of adhesive in the presence of a plasticizing liquidmore volatile than water; and applying heat directly to the glue linethereby driving the plasticizing liquid away from the glue line,

, whereby a very rapid setting of the gl results. l 9. In the process ofrapidly edge gluing one sheet of wood to another, the step of adding asa plasticizing liquid, :1 liquid more volatile than water whereby thesetting period of the glue is shortened. 10. As an article ofmanufacture, a sheet comprising a plurality of sheets of wood veneer ina substantially wet, saturated, green condition, and joined along theirmarginal edges.

11. In a device of the character described the combination of asupporting surface on which may be brought together two pieces of wood;means for removing accidental adhesive base powder deposited on the faceof the pieces; and a heating means relatively movable as respectssaidpieces of wood and said supporting surface.

12. As an article of manufacture, a wood fabrication composed of two ormore wood pieces united along their marginal edges by a bond resultingfrom the rapid application of heat directly to the glue line after theforming of said glue line by undispersed discrete particles of adhesivein the presence of sufiicient liquid to plasticize the adhesive materialsufiiciently for the formation of the bond, identifiable discreteparticles of adhesive remaining between said marginal edges.

13. As an article of manufacture, a continuous sheet of green veneercomposed of two or more pieces of green veneer united along theirmarginal edges by a bond resulting from the rapid application of heatdirectly to the glue line after the forming of said glue line byundispersed discrete particles of adhesive in the presence of sufficientliquid to plasticize the adhesive material.

14. As an article of manufacture, a wood fabrication composed of two ormore wood pieces united along their marginal edges by a bond resultingfrom the rapid application of heat directly to the glue line after theforming of said glue line by undispersed discrete particles of adhesivein the presence of sufficient water to plasticize the adhesive materialsufficiently for the formation of the bond, identifiable discreteparticles of adhesive remaining between said marginal edges.

15. As an article of manufacture, a continuous sheet of green veneercomposed of two or more pieces of green veneer united along theirmarginal edges by a bond resulting from the rapid application of heatdirectly to the glue line after the forming of said glue line byundispersed discrete particles of adhesive in the presence of sufiicientwater to plasticize the adhesive material sulficiently for the formationof the bond, identifiable discrete particles of adhesive remainingbetween said marginal edges.

16. As an article of manufacture, a wood j fabrication composed of twoor more wood pieces united along their marginal edges by a bondresulting from the rapid application of heat directly to the glue lineafter the forming of said glue line by undispersed discrete particles ofadhesive in the presence of sufiicient plasticizing liquid more volatilethan water to plasticize the adhesive material sufliciently for theformation of the bond, identifiable discrete particles of adhesiveremaining between said marginal edges.

17. As an article of manufacture, a continuous sheet of green veneercomposed of two or more pieces of green Veneer united along theirmarginal edges by a bond resulting from the rapid application of heatdirectly to the glue line after the forming of said glue line byundispersed discrete particles of adhesive in'the presence of sufiicientplasticizing liquid more volatile than water to plasticize the adhesivematerial sufficiently for the formation of the bond, identifiablediscrete particles of adhesive remaining between said marginal edges.

18. The process of rapidly edge gluing one piece of wood to anothercomprising a contact of one of the edges to be joined with undisperseddiscrete particles of adhesive in the presence of a plasticizing medium;bringing together the edges to be joined, applying pressure and heat tothe glue line.

19. The process of rapidly edge gluing one piece of wood to anotherwhich comprises applying to one of the edges to be glued, an adhesivematerial in dry powdered form, causing the plasticization of thematerial and subjecting the material to bonding conditions in thepresence of heat.

20. The process of rapidly edge gluing one piece of wood to anotherpiece comprising contacting one of the edges to be joined withundispersed discrete particles of adhesive in the presence of sufficientliquid to plasticize the adhesive material; bringing together the edgesto be joined; and applying heat directly to the glue line, whereby themoisture is driven away from the glue line.

21. The process of rapidly edge gluing one piece of wood to anotherwhich comprises providing at a glue line between the edges to be gluedan adhesive material in discrete particle form and a plasticizing liquidand applying heat directly to the glue line.

22. The process of rapidly edge gluing one piece of wood to anotherwhich comprises providing at a glue line between the edges to be gluedan adhesive material in dry powdered form and a plasticizing liquid andapplying heat directly to the glue line.

23. The process of rapidly edge gluing one piece of wood to anotherwhich comprises providing at a glue line between the edges to be gluedan adhesive material in discrete particle form and a plasticizing liquidand plasticizing chemicals and applying heat directly to the glue line.

24. The process of rapidly edge gluing one piece of wood to anotherwhich comprises providing at a glue line between the edges to e glued anadhesive material in dry powdered form and a plasticizing liquid andplasticizing chemicals and applying heat directly to the glue line. i

25. The process of rapidly edge gluing one piece of wood to another onecomprising applying heat directly to the glue line on which the adhesiveparticles are present in discrete form.

26. The process of rapidly edge gluing one piece of wood to another onecomprising applying heat directly to the glue line on which the adhesiveparticles are present in discrete form in the presence of a plasticizingliquid.

27. The process of rapidly edge gluing one piece of wood to another onecomprising applying heat to the glue line on which the adesive particlesare present in discrete form in the presence of a plasticizing liquid insuch manner that the action of the heat drives the plasticizing liquidaway from the glue line.

28. A process of rapidly edge gluing one piece of wood to another piececomprising the steps of providin discrete adhesive together wit aplasticizing agent upon at least one of the edges to be jolned andbringing the members into contact in a heating zone whereby abond isformed.

29. The process of rapidly edge gluing which comprises contacting one ofthe edges to be glued with'discrete particles of an adhesivecharacterized by being plasticized by a liquid and rendered insoluble byheating, and contacting the edges to be glued in the resence of theplasticizing liquid and subecting to bonding conditions whereby a waterresistant bond is produced.

30. The process of rapidly edge gluing which comprises contacting one ofthe edges to be glued with casein in discrete article form and bringingthe edges to be g ued together in the presence of a plasticizin'g liquidand subjecting to bonding conditions whereby a water resistant bond isroduced.

31. The process of rapid y edge gluing which comprises contacting one ofthe edges to the glue with' discrete particles of adhesive characterizedby being plasticized by a liquid and a chemical, and rendered insolubleby heating and bringing together the edges to be glued in the presenceof the plasticizing liquid and chemical and subjecting the whole tobonding conditions whereby a water resistant bond is produced.

32. The process of rapidly edge gluing two pieces of wood comprising thesteps of applying an adhesive in discrete particle form to at. least oneof the edges to be joined in the a presence of a plasticizing liquid,and conarticles of tacting the edges of the pieces of wood, re-

moving adhesive in the dry particle form acoldentally deposited on thesurfaces of the pieces of wood adjacent to the edges and applying heatdirectly to the glue line whereby a bond is formed with the adjacentface portions of the pieces of wood clean.

33. The process of uniting members, which comprises associating Woodsections edge to edge with interposed adhesive material indiscrete-particle form, and subjecting to bondin conditions.

34. he process of uniting members, which comprises associating woodsections edge to edge with interposed adhesive material indiscrete-particle form, and holding the edges together while applyingheat directly to the glue line;

35. The process of unitin members, which comprises associating woosections edge to edge with interposed adhesive material indiscrete-particle form, and holding the edges togetherwhile applyingheat directly to both sides of the glue line.

36. The process of uniting members, which comprises associating woodsections edge to edge with interposed adhesive material indiscrete-particle form, and holding the edges together while applyingheat directly to the glue line in a continuous manner commencmg at oneend of the glue line and ending at the other end.

37. The process of unitinq members, which comprises associating wet woodsections edge to edge with interposed adhesive material indiscrete-particle form, and subjecting to bonding conditions.

38. The process of uniting members, which comprises associating wet woodsections edge to edge with interposed adhesive material indiscrete-particle form, and holding the edges together while applyingheatdirectly to the glue line. 7

39. The process of uniting members, which comprises applying adhesivematerial in powdered form to the edge of a wet wood section, associatingthe edge of another section, and subjecting to heat and pressure.

40. The process of rapidly edge gluing one sheet of wood to anothersheet of wood, comrising contacting one of the edges to be oined withundispersed discrete articles of adhesive, bringin together on a iieatedsupporting surface t e edges to be joined, and applying heat to the oposite side of the g no line while holding 41. The process of unitinmembers, which comprises-associating woo sections edge to edge withinterposed adhesive material in powder-form, and subjecting to bondingconditions.

In witness whereof, we hereunto subscribe our names August, 1929.

THEODORE WILLIAMS DIKE. CHARLES N. CONE.

t e edges together

